1. Field of the Invention
The present invention generally relates to a roller for a clinker grinder. More specifically, the present invention relates to an attachment for a clinker grinder roller to a related drive shaft.
2. Description of the Related Art
Large coal burning power plants and furnaces produce ash as a combustion byproduct. The ash typically accumulates as a powder and in large chunks referred to as “clinkers.” A clinker grinder machine is used to grind the ash clinkers into small particles so that the ash can be transported for disposal through pipes pneumatically or hydraulically. Clinker grinders typically have one or two large drum rollers with grinding teeth on the surface of the rollers. The rollers are rotated so that the grinding teeth grind the clinkers. Clinker grinder machines operate in a hot, corrosive, and erosive environment and experience severe operating loads, yet must operate for long periods without failure. A particularly difficult design challenge is providing an attachment between the grinder roller and the drive shaft that rotates the roller. The roller grinding surfaces are typically formed of very hard abrasion-resistant alloyed cast iron. This class of cast irons is virtually unweldable, so welding a roller made of such alloys to the driving shaft is not an option. To address the design challenges, current common practice is to attach the clinker grinder roller to the rotatable drive shaft via an insert plate to form a grinder roller assembly. The current insert plates have sharp-edged outer surfaces, for example hexagonally shaped. When torque is applied to the shaft, the shaft rotates the insert plate and the grinder roller assembly.
Currently, the clinker grinder roller is made by independently casting the grinder roller. The insert plate with its outer sharp edges is separately formed and machined. The sharp-edged insert plate is pressed into roller end cavities. The drive shaft is then inserted through the insert plate and the roller, after which the shaft is welded to an inner surface of the insert plate. Finally, shims are inserted between the insert plate and the roller to position the shaft at the center of the roller. The shims are then welded to the outer surface of the insert plate to secure them in place.
This presently available roller manufacturing process results in several shortcomings. First, the outer surface of the insert plate tends to pulls away from the inner surface of the clinker grinder roller during the welding of the shaft to the insert plate which can loosen the attachment between the insert plate and the roller. Second, the shims eventually wear and loosen. Third, since the roller cavity is a cast, in most cases the inner surfaces of the roller cavity are not flat which reduces the load bearing area between the insert plate and the roller. These three problems cause the clinker grinder roller to disengage from the insert plate, creating a loose fit which eventually leads to the failure of the device.